Histology Lecture #17: Blood

Specialized connective tissue.

What type of tissue is blood classified as?

Blood formed elements.

What are the cellular components of blood called?

1. Erythrocytes (red blood cells)

2. leukocytes (white blood cells)

3. platelets (thrombocytes)

What are the three main types of blood formed elements (cells)?

Plasma

What is the extracellular component of blood?

5L

What is the average volume of blood in the human body?

1. Transport

2. Protection

3. Defense

What are the three main functions of blood?

• Delivery of nutrients and oxygen directly or indirectly to cells

• Transport of wastes and carbon dioxide away from cells

What is the transport fuction of blood?

• Maintenance of homeostasis by acting as a buffer and participating in coagulation and thermoregulation

What is the protection fuction of blood?

• Transport of humoral agents and cells of the immune system that protect the body from pathogenic agents, foreign proteins, and transformed cells

What is the defense fuction of blood?

1. Water: 92%

2. Proteins: 7%

- Albumins: 58%

- Globulins: 37%

- Fibrogen: 4%

- Regulatory proteins <1%

3. Other solutes: <1%

- Electrolytes

- Nutrients

- Respiratory gases

- waste products

What makes up the composition of plasma (55% of whole blood)?

44%

- 4.2-6.2 million per cubic cm

What percentage of whole blood is Erythrocytes?

1. Platelets

- 150-400 thousand per cubic mm

2. Leukocytes

- Neutrophils

- Lymphocytes

- Monocytes

- Eosinophils

- Basophils

What makes up the composition of the buffy coat? (<1% of whole blood)

The volume of packed erythrocytes in a sample of blood.

What does hematocrit measure?

As a percentage (ratio of red blood cells per volume of blood).

How is hematocrit expressed?

By centrifuging a blood sample with anticoagulant in a calibrated tube.

How is hematocrit obtained?

Males: 42%

Females: 38%

What is the normal hematocrit value for males and females?

An aqueous solution.

What is plasma?

Normal range: 7.35 - 7.45

Average: 7.4

What is the normal pH range and average range of plasma?

Terminally differentiated cells.

What type of cells are erythrocytes?

No, they lack nuclei and organelles.

Do erythrocytes have nuclei and organelles?

Hemoglobin, giving them acidophilia.

What fills the cytoplasm of erythrocytes?

Flexible biconcave discs. 7.5 µm diameter.

What is the shape and diameter of erythrocytes?

3.9–5.5 million per microliter (µL or mm³).

What is the normal erythrocyte count for women?

4.1–6.0 million per microliter (µL).

What is the normal erythrocyte count for men?

A cup-like shape.

What shape do erythrocytes adopt at capillary bifurcations?

Rouleaux

What are stacks of erythrocytes in larger blood vessels called?****

The presence of hemoglobin (Hb).

What causes the cytoplasmic acidophilia of erythrocytes?

Oxygen: Oxyhemoglobin.

Carbon dioxide: Carbaminohemoglobin.

What compound is formed when hemoglobin binds to oxygen or carbon dioxide?

Approximately 120 days.

What is the average lifespan of an erythrocyte?

- 40% lipids

- 10% carbohydrates

- 50% proteins

What are the main components of the erythrocyte cell membrane and their approximate percentages? (3)

Integral proteins.

What type of proteins make up most of the erythrocyte membrane proteins?

Ion channels, the anion transporter band 3 protein, and glycophorin A.

What are examples of integral proteins in the erythrocyte membrane? (3)

They contain antigenic domains that form the basis of the ABO blood group system.

What is the function of glycophorin A’s glycosylated extracellular domains in erythocytes?

4,500 to 11,000 cells per microliter (μL).

What is the normal leukocyte count in blood?

In the tissues.

Where do leukocytes become functional?

Immune functions.

What is the main function of leukocytes?

They have very pale and numerous cytoplasmic granules.

How are leukocytes characterized in terms of cytoplasmic appearance?

Plasma: Spherical

Tissues: Mobile and amoeboid

What is the shape of leukocytes when suspended in plasma and in tissues?

1. Lysosomes (azurophilic granules)

2. Specific granules with specific functions.

What type of cytoplasmic granules do granulocytes contain? (2)

1. Neutral (neutrophils)

2. Basic (basophils)

3. Acidic (eosinophils).

What are the three types of specific granules in granulocytes and their corresponding cells? (3)

Polymorphic nuclei.

What type of nucleus do granulocytes have?

Only azurophilic granules.

What type of granules do agranulocytes contain?

Spherical or indented.

What is the shape of the nucleus in agranulocytes?

1. Lymphocytes

2. Monocytes

What are the two types of agranulocytes?

Netrophils > Lymphocytes > Monocytes > Eosinophils > Basophils

"Never Let Monkeys Eat Bananas"

What is the order of increasing abundance of Leukocytes?*** (he said to know this)

50-70%.

What percentage of circulating WBCs are neutrophils?

Two to five lobules with thin extensions.

How many lobules do neutrophil nuclei have?

Barr body (condensed inactive X chromosome).

What unique nuclear feature can be seen in female neutrophils?

Neutrophils

Which WBC usually arrives first at infection sites?

6–8 hours in blood; 1–4 days in connective tissue before dying by apoptosis.

What is the lifespan of neutrophils in blood and connective tissue?

Granular and pale-stained.

How is the cytoplasm of neutrophils stained?

1. Azurophilic granules (lysosomes)

2. Specific (secondary) granules.

What are the two types of cytoplasmic granules in neutrophils?

Large and dense; involved in killing and degradation of microorganisms.

What are the characteristics and function of azurophilic granules?

Smaller, less dense, stain light pink; have multiple functions.

What are the characteristics and function of specific (secondary) granules?

Kill and degrade phagocytosed microorganisms.

What is the function of azurophilic granules in neutrophils?

Myeloperoxidase (MPO).

What enzyme in azurophilic granules generates hypochlorite and other agents toxic to bacteria?

Lysozyme.

What enzyme in azurophilic granules degrades components of bacterial cell walls?

Small cysteine-rich proteins that bind and disrupt the cell membranes of many types of bacteria and other microorganisms.

What are defensins, and what is their function in azurophilic granules of neutrophils?

Secretion of ECM-degrading enzymes, such as collagenases.

What is one function of neutrophil specific granules related to the extracellular matrix?

They deliver other bactericidal proteins to phagolysosomes.

How do specific granules contribute to killing bacteria inside phagolysosomes?

They insert new cell membrane components.

What role do specific granules have in neutrophil cell membranes?

Multilobulated, with peripheral heterochromatin and central areas of euchromatin not in contact with the nuclear envelope.

Describe the nucleus of neutrophils.

1-4%.

What percentage of circulating WBCs are eosinophils?

Similar or slightly larger than neutrophils.

How does the size of eosinophils compare to neutrophils?

Bilobed

What is the shape of the eosinophil nucleus?

Large acidophilic specific granules, pink to red in color.

How is the cytoplasm of eosinophils characterized?

Oval, with flattened crystalloid cores.

What is the shape of eosinophil granules?

Major basic protein (MBP), an arginine-rich factor that makes up 50% of granule protein and accounts for acidophilia.

What is the major content of eosinophil granules?

Kill helminths together with other enzymes.****

What is the function of eosinophil granules in parasitic infections?*****

By releasing chemokines, cytokines, and lipid mediators.

How do eosinophils modulate inflammation in allergies?

Less than 1%.

What percentage of circulating WBCs are basophils?

Similar in size.

How does the size of basophils compare to neutrophils and eosinophils?

Bilobed

What is the shape of the basophil nucleus?

Large, irregular, basophilic (very dark), and electron-dense.

How are basophil cytoplasmic granules characterized?

1. Heparin and other sulfated GAGs (acidophilia)

2. Histamine

3. Phospholipase A

4. Other mediators of inflammation.

What are the key contents of basophil granules? (4)

Function similar to mast cells.

How are basophil functions related to other immune cells?

Receptors for IgE.

What specific surface receptors do basophils have?

Lymphocytes (20-40% of circulating WBC's)

What are the most numerous agranulocytes?

By antibodies (immunohistochemistry) and flow cytometry

How can lymphocytes be identified in the lab?

Smallest leukocytes; generally have a spherical nucleus

What is the size and nucleus shape of lymphocytes?

B cells, T cells, NK cells

What are the main classes of mature lymphocytes? (3)

Outside the bone marrow

Where do T cells differentiate?

Natural killer (NK) cells (together with other activated lymphocytes)

Which lymphocytes are the largest?

Small lymphocytes

Which lymphocytes are the most numerous?

Spherical

What is the shape of the nucleus in small lymphocytes?

Condensed chromatin (heterochromatin)

What type of chromatin do small lymphocytes have?

Thin rim of surrounding cytoplasm

Describe the cytoplasm of small lymphocytes.

Larger than erythrocytes

How do larger lymphocytes compare in size to erythrocytes?

Larger and slightly indented

Describe the nucleus of larger lymphocytes.

More cytoplasm, slightly basophilic

How does the cytoplasm of larger lymphocytes appear?

Few azurophilic granules

What granules are present in larger lymphocytes?

2% - 8% of circulating WBCs

What percentage of circulating WBCs are monocytes?

Macrophages and other cells of the mononuclear phagocytic system

What cells do monocytes give rise to?

They are antigen-presenting cells (APCs)

What is a functional characteristic of ALL monocyte-derived cells?****

Monocytes

What are the LARGEST leukocytes? ***

Large, indented or C-shaped

Describe the nucleus of monocytes.

Basophilic with many small lysosomal azurophilic granules

Describe the cytoplasm of monocytes.

Small membrane-bound cell fragments

What are platelets?

No, they are anucleated

Do platelets have a nucleus?

Giant cells called megakaryocytes

From which cells do platelets derive from?